Means for interrupting electric circuits



Aug. 16, 1932. A. LOTZ 72 MEANS FOR INTERRUPTING ELECTRIC CIRCUITS FiledMarch 27, 1931 min/5555 INVENTOR 4 yw i/brfAofZ Y 2 A'II'TORNEY PatentedAug. 16, 1932 UNITED STATES PATENT; OFFICE ALBERT Lo'rz, ornnaLm-smmanssranr,

GERMANY, .ASSIGNOR o .WESTIN'GHOUSE ELECTRIC & MANUFACTURING COMPANY,A'coarom'rIoN or PENNSYLVANIA mans on rmimnurrmo ELECTRIC crncurrsApplication 'flled um a1, 1931, Serial No. 525,679, and a Germany March27, 1030.

My invention relates to an electric-circuit interrupter and,particularly, toelectric-circuit interrupters utilizing porous objectsfilled with conducting fluid which will be evaporated by the heat of thecurrent flowing therethrough. e

It is an object of m invention to utilize the heat of the current owingthrough a porous resistanceimpregnated by a conducting 1o liquid to evaorate the liquid and thereby interrupt the ow of current. V I c It is afurther object of the invention to provide a circuit interrupter whichwill be cheap to manufacture and which will have no moving parts.

It is a still further object of the invention to provide a circuitinterrupter havin no mtiying parts but which may be varie at w1 vso Itis an ancillary object of the invention to provide a device which may beutilized as a circuit breaker per se, as'a time delay switch or as anoverload relay.

It is another object of the. invention to so construct a resistanceliquid switch that gases formed by electrolysis at the electrodes willbe unable to break down electrically and, therefore, will not causearcing.

Other objects and advantages of the invention will become apparent fromthe following description and drawing, wherein The single figure is across-sectional view of a preferred embodiment of my invention, showmg aporous insulating mass, the capili lary spaces of which are filled witha liquid.

For interrupting a hi h-tension circuit without the formation 0 an arc,switches have been proposed in which a liquid resistance is graduallyintroduced into the circuit to be broken. Precautions must be taken toprevent the formation of gas or vapor between or at the electrodesbecause the gas pockets would break down and cause the formation of anarc in the liquid between the electrodes.

According to this invention, the formation of an arc is to be preventedby introducing into the circuit a body of porous insulating material,the pores of which are filled with a resistance liquid. A gradualincrease in resistance will, according to the invention, result from thefact that the liquid in the pores will be evaporated by the heatingeffect of, the current. Vapor formation between the electrodes will notlead to the formation of an arc, in this case, because an arc cannotexist in the capillary spaces. 1 The greatest difficulties in theseresistance liquid switches are met with at the electrodes, since thecurrent density reaches its highest value at these points. Gases areformed'by electrolysis and these easily break down electrically. Whenwater or aqueous solutions are used, hydrogen is formed at the cathode.According to the invention, these difiicultiesare avoided by sodesigning the porous bodyfthat the cross section is smaller in the partbetween the electrodes than it is at the electrodes. vaporization willoccur at the point of maximum current density, which, in this case, issome distance away from the electrodes. While a gas which is formed atthe electrode will break down immediately in the electron stream emittedby the glowing cathode,ithe gas volume, in the present instance, issurrounded by liquid and, therefore, will not become ionized. I i

The porous insulating material which i used may be burned clay, loosesand or any otherisuitablematerial. Pure water may be used fortheliquid. To increase the conductivity of theliquid, it is mostdesirable to add substances which will vaporize with the liquid andleave no conducting residue. 1 Substances of this kind are ammonia,nitric acid, formic'acid, etc. a

Referringspecifically to the drawing, one example of the device, whichis the sub ect of this application, is shown.

Numeral 10 designates the porous, insulating mass, the capillary spacesof which are are provided with disconnect switches 13 and 14. A switch15 is provided to short circuit the porous mass 10.

Current interruption proceeds in the following manner.

First, the main switch 15 is opened. This throws the porous mass 10,filled with a liquid conductor 9, into tne circuit. The resistance ofthe liquid must not be too high, in comparison with the resistance ofthe other portions of the circuit.

T he current then flows through the liquid contained in the porous mass10, and the liquid will start to evaporate at the constricted section16, which is the point of greatest current density. The vaporization isgradual and the resistance of the conductor increases constantly. Theresistance at the electrodes 17 and 18 remains relatively small. \Vhenthe liquid, in a certain length of the cylindrical portion of the bodyat the point- 16, has been entirely vaporized, current interruption iscomplete. Arc formation cannot occur for the reasons already mentioned.

After the circuit has been broken, the switches 13 and 14 carry nocurrent but must be opened because liquid will be drawn up into thesection where the currentwas interrupted and this would again close thecircuit.

The porous body 10 may be filled with the conducting switching liquid 9by immersing it in a vessel containing the liquid. It may then beremoved and placed on the electrodes for use. Other means may be used tokeep the vaporization away from the electrodes; for instance, certainportions at a distance from the electrodes may be preheated.

From the foregoing description, it will readily be seen that I haveconstructed a liquid-resistance switch which may be cheaply and easilymanufactured and which will have no moving parts. The interrupter may bevaried at will by keeping the ends immersed in a predetermined amount ofliquid.

The invention may be used as a circuit breaker, as described, or as atime switch by determinin first the time taken under a specified set ofconditions for causing current interrupt-ion. t may also be used as atime overload relay by so balancing the constituent parts thatevaporation will not occur until a predetermined maximum current isattained.

It is also obvious that the disadvantages of liquid-resistance switchesare overcome by placing the porous mass in the circuit VhQI'Q. by gasesgenerated by the electrolysis around the electrodes, which willordinarily break down electrically at a low current value, will not beable to break down since it will be disseminated throughout the porousmass.

Although I have shown and described a specific embodiment of myinvention, it will be understood that modifications and changes may bemade by those skilled in the art without departing from the spirit andscope of the appended claims.

I claim as my invention:

1. A device for interrupting electric currents in a. circuit comprisinga pair of electrodes, aresistance connected across the electrodescomprising a resistance liquid and a porous body of insulating material,said body being placed between said electrodes and being at least partlyfilledwith said liquid'to conduct current, the cross section of saidporous body being less at the points between the electrodes than at theelectrodes.

2. A device for interrupting electric currents in a circuit comprising apair of electrodes, a resistance connected across the electrodescomprising a resistance liquid and a porous body of insulating material,said body being placed between said electrodes and at least partlyfilled with said liquid toconduct current, said liquid being such thatit evaporates withoutleaving a substantial residue.

3. A device for interrupting electric currents in a circuitcomprising aplurality of electrodes, a resistance connected across the electrodescomprising vessels filled with resistance liquid and a porous body ofinsulating material, said porous body being placed between saidelectrodes and at least partly impregnated by said liquid for conductingcurrent, the cross section of said body being less at the points betweenthe electrode than at the electrodes, the ends of said porous body beingdisposed in vessels filled with liquid.

In testimony whereof, I have hereunto subscribed my name this 7th day ofMarch. 1931.

' ALBERT LOTZ.

